Sensors are used for the testing and diagnosis of diesel engines equipped with conventional injection systems. These internal combustion engines often have no electrical means that would enable a simple and rapid determination of, for example, the RPM, the beginning of fuel conveyance and the injection pressure curve, which are all important for the recognition of errors in the injection system that often result in impermissibly poor exhaust values. Thus, there is a need for economical, rugged and sufficiently precise sensors that can be attached to the internal combustion engine easily and rapidly and that permit such measurements.
Sensors whose designs are somewhat suited for these purposes, having various features, are known for example from the following letters patents: AT-PS 375.466, AT-PS 353.507, AT-PS 373.393, AT-PS 373.394, AT-PS 374.007, AT-PS 374.280. In addition, for example DE 40 02 790 C2 is also known, which also refers to some of the documents named above.
However, all known sensors of this type are relatively expensive, due to their construction and the parts used. In addition, the thin metallic protective film used for the frictionally engaged connection between the injection line tube and the measuring element is extremely fragile. Therefore, an injection line must be polished before the sensor is clamped in place. Burrs and dirt must be removed, and further, any protective layer or coat of lacquer that may be present must also be removed because this layer not only causes an enlargement of the tube diameter that is impermissible for the use of the known sensors, but also prevents the required electrical contact of the sensor to the engine frame.
The object of the invention is to avoid the mentioned disadvantages of the known sensors, and to indicate a sensor of the type named above that is simple and durable, that can be used even on painted lines, and that above all is also economical due to its manner of construction, while nonetheless maintaining good measurement characteristics.